[Wgesnerjr]

Welcome!
I have done this. My wife insisted on a seat with headrests. I found what was the nastiest seat from 89 pickup at the junk yard. The 89 sliders would not work on our floor. (there is much more room between the floor and the seat bottom on the 89) I used the stock 85 seat sliders but had to cut them down as they are much longer than the seat bottom from the 89.

All in all the seat works but I think the 86 had a thinner backrest and longer seat bottoms. However, the 89 foams are more contoured. (almost like bucket seats) If I had to do it over again, I would probably look at welding in the headrest mounts into the 85 seat frame.